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The radius of the observable universe is therefore estimated to be about 46.5 billion light-years. [8] [9] Using the critical density and the diameter of the observable universe, the total mass of ordinary matter in the universe can be calculated to be about 1.5 × 10 53 kg. [10]
an object of diameter 1 AU (149 597 871 km) at a distance of 1 parsec (pc) Thus, the angular diameter of Earth's orbit around the Sun as viewed from a distance of 1 pc is 2″, as 1 AU is the mean radius of Earth's orbit. The angular diameter of the Sun, from a distance of one light-year, is 0.03″, and that of Earth 0.0003″. The angular ...
The great majority of ordinary matter in the universe is unseen, since visible stars and gas inside galaxies and clusters account for less than 10 percent of the ordinary matter contribution to the mass–energy density of the universe. [120] [121] [122] Ordinary matter commonly exists in four states (or phases): solid, liquid, gas, and plasma ...
This is related to the angular diameter distance, which is the distance an object is calculated to be at from and , assuming the Universe is Euclidean. The Mattig relation yields the angular-diameter distance, d A {\displaystyle d_{A}} , as a function of redshift z for a universe with Ω Λ = 0.
It represents the boundary between the observable and the unobservable regions of the universe, so its distance at the present epoch defines the size of the observable universe. Due to the expansion of the universe, it is not simply the age of the universe times the speed of light, as in the Hubble horizon, but rather the speed of light ...
Maximum diameter of Thiomargarita namibiensis, the second largest bacterium ever discovered 10 −3: 1 millimeter ~5 mm Length of an average flea is 1–10 mm (usually <5 mm) [27] 2.54 mm One-tenth inch; distance between pins in DIP (dual-inline-package) electronic components 5.70 mm Diameter of the projectile in 5.56×45mm NATO ammunition 10 −2
In modern physical cosmology, the cosmological principle is the notion that the spatial distribution of matter in the universe is uniformly isotropic and homogeneous when viewed on a large enough scale, since the forces are expected to act equally throughout the universe on a large scale, and should, therefore, produce no observable inequalities in the large-scale structuring over the course ...
If k is positive, then the universe is "closed": starting off on some paths through the universe return to the starting point. Such a universe is analogous to a sphere: finite but unbounded. If k is negative, then the universe is "open": infinite and no paths return. If k = 0, then the universe is Euclidean (flat) and infinite. [4]: 69